JP2686235B2 - Imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solid-state image pickup device (C
The present invention relates to an image pickup apparatus such as a video camera using a CD or the like.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a configuration example of a conventional image pickup apparatus. In FIG. 4, 1 is a lens, 2 is a diaphragm device, 3 is a CCD, 4 is a sampling circuit, 5 is a signal processing circuit, 6 is a comparator, 7 is a threshold value setting device for comparison, and 8 is a comparator.
Indicates an integrating amplifier, and 9 indicates a control circuit.

The light emitted from the subject is condensed by the lens, passes through the diaphragm device 2, and reaches the light receiving surface of the CCD 3. The CCD 3 converts into an electric signal of a level (for example, several mV to several tens of mV) according to the amount of received light, and outputs the electric signal to the sampling circuit 3. In the sampling circuit 3, the input electric signal is sampled under the control of the control circuit 9, and the signal subjected to the sampling process is input to the signal processing circuit 5. Then, the signal processing circuit 5 performs a predetermined process to generate a video signal, which is output as a video output and also output to the comparator 6.

In the comparator 6, when the sampling signal S91 from the control circuit 9 is inputted, the so-called photometric value, which is the video signal S5 from the signal processing circuit 5, and the comparison threshold value setting device 7 are set in advance. The level is compared with the threshold value Vth, and the signal S6 corresponding to the difference is output to the integrating amplifier 8. This comparison process is performed at the same timing as the sampling timing of the sampling circuit 4. The integration amplifier 8 performs integration and amplification processing on the signal S6, and outputs the control signal CTL to the drive motor 2a of the diaphragm device 2.

As a result, as a result of the comparison process of the comparator 6,
For example, the photometric value according to the amount of light received by the CCD 3 is the threshold value V
If it is larger than th, the diaphragm operation control (negative processing) is performed assuming that the amount of incident light is large. On the contrary,
When the photometric value is smaller than the threshold value Vth, the opening operation control (positive processing) is performed assuming that the incident light amount is small.

[0006]

However, in the above-mentioned conventional image pickup apparatus, since the processing speed is high, a difference occurs between the drive time of the motor 2a to be controlled and the control time of the integrating amplifier 8 to be controlled. So, so-called over-aperture,
Alternatively, there is a problem that under-drawing occurs, and as a result, a hunting phenomenon occurs.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image pickup apparatus capable of preventing the occurrence of a hunting phenomenon by eliminating the over and under diaphragms.

[0008]

In order to achieve the above object, the image pickup apparatus of the present invention has a diaphragm means for adjusting the quantity of light passing therethrough according to a control signal, and a quantity of light received by receiving light passing through the diaphragm means. An image sensor that generates an electrical signal of a level according to the above, a sampling unit that performs a sampling process on the electrical signal by the image sensor, and an electrical signal level that has undergone the sampling process at the sampling timing and a preset signal level are compared. And a comparing means for outputting a signal according to the result, a calculating means for obtaining a difference between the output signal of the comparing means and the control signal, and an integrating means for performing an integration process on the output signal of the calculating means. ,
A signal holding means for holding the output signal of the integrating means during the input period of the hold signal and outputting it as the control signal to the aperture means and the arithmetic means when the input of the hold signal is stopped, and for the next sampling period, input Control means for outputting the holding signal to the signal holding means so as to hold the signal.

[0009]

According to the image pickup apparatus of the present invention, the light emitted from the subject passes through the diaphragm means and reaches the light receiving surface of the image pickup element. In the image pickup device, it is converted into an electric signal having a level corresponding to the amount of received light and is output to the sampling means. The sampling means performs sampling processing on the input electric signal, and the signal subjected to the sampling processing is output to the comparing means. The comparison means compares the electric signal level subjected to the sampling process with the preset signal level at the sampling timing, and outputs a signal corresponding to the result to the arithmetic means. The arithmetic means obtains the difference between the output signal of the comparing means and the control signal, outputs the difference to the integrating means, and after performing a predetermined integration process here, outputs the signal to the signal holding means. The signal holding unit holds the input signal during the input period of the holding signal output from the control unit. Then, when the input of the holding signal is stopped, the held signal is output as a control signal to the diaphragm means and the arithmetic means. In this way, the output control signal of the signal holding means is fed back to the arithmetic means, the addition processing with the output signal of the comparison means is performed at the time of the next sampling completion, and the integration means integrates it. Alternatively, the occurrence of under diaphragm is suppressed.

[0010]

1 is a block diagram showing an embodiment of an image pickup apparatus according to the present invention, and the same components as those in FIG. 4 showing a conventional example are represented by the same reference numerals. That is, 1 is a lens,
2 is a diaphragm device, 3 is a CCD (solid-state imaging device), 4 is a sampling circuit, 5 is a signal processing circuit, 6 is a comparator, and 7
Is a comparison threshold setting device, 8 is an integrating amplifier, 9a is a control circuit, 10 is an adder, and 11 is a holding amplifier.

The control circuit 9a controls the operations of the CCD 3, the sampling circuit 4, the signal processing circuit 5 and the comparator 6, and also outputs the sampling signal S91 to the comparator 6 to the holding amplifier 11. Hold signal for only period S92
Is output to stop the signal output, and the output signal S8 of the integrating amplifier 8 is held during that period.

The adder 10 adds the output signal S6 of the comparator 6 and the control signal CTL output from the holding amplifier 11, specifically, finds the difference between the two signals and outputs it as the signal S10 to the integrating amplifier 8. .

The holding amplifier 11 holds the output signal S8 of the integrating amplifier 8 during the input period of the holding signal S92 output from the control circuit 9a, and when the input of the holding signal S92 is stopped, the held signal is held. The control signal CTL is output to the drive motor 2a and the adder 10.

Next, the operation of the above configuration will be described. The light emitted from the subject is condensed by the lens, passes through the diaphragm device 2, and reaches the light receiving surface of the CCD 3. The CCD 3 has a level (for example, several mV to several tens of m) depending on the amount of received light.
V) is converted into an electric signal and output to the sampling circuit 4. The sampling circuit 4 performs sampling processing on the input electric signal under the control of the control circuit 9a, and the signal subjected to the sampling processing is processed by the signal processing circuit 5
Is input to Then, the signal processing circuit 5 performs a predetermined process to generate a video signal, which is output as a video output and also output to the comparator 6.

In the comparator 6, when the sampling signal S91 from the control circuit 9a is input, the so-called photometric value, which is the video signal S5 from the signal processing circuit 5, and the comparison threshold value setting device 7 are set in advance. The level is compared with the threshold value Vth, and the signal S6 corresponding to the difference is output to the adder 10. In the adder 10, the output signal S6 of the comparator 6 and the control signal C output from the holding amplifier 11
An addition process with TL is performed, and a signal S10 corresponding to the difference between the two signals as a result is output to the integrating amplifier 8. The integrating amplifier 8 performs integration and amplification processing on the signal S6, and outputs the signal S8 to the holding amplifier 11.

In the holding amplifier 11, the integrating amplifier 8
Output signal S8 is held during the input period of hold signal S92 output from control circuit 9a. Then, the hold signal S92
When the input of is stopped, the signal held is changed to the control signal C
It is output as TL to the drive motor 2a and the adder 10. In this way, the output control signal CTL of the holding amplifier 11
Is fed back from the adder 10, and when the next sampling is completed, addition processing with the output signal S6 of the comparator 6 is performed and integrated by the integrating amplifier 8. Therefore, since the integrated value is added to the feedback control signal CTL, the amount of change is smaller than when starting from zero,
As a result, it converges.

As a result, as a result of the comparison process of the comparator 6,
For example, the photometric value according to the amount of light received by the CCD 3 is the threshold value V
If it is larger than th, the diaphragm operation control (negative processing) is performed assuming that the amount of incident light is large. On the contrary,
When the photometric value is smaller than the threshold value Vth, the opening operation control (positive processing) is performed assuming that the incident light amount is small.

In practice, as shown in FIGS. 2 and 3,
During the sampling period, a constant value is held so that the operation is stopped after the diaphragm device 2 is narrowed down, and by adding the value of the next sampling, the opening / closing operation with the output signal S6 of the comparator 6 is performed. The operation period shown in FIG. 2 is shortened or shortened depending on the operation speed of the control circuit 9a. further,
In FIG. 3, the curve indicated by C indicates the actual light amount, and the curve indicated by D indicates the control curve.

As described above, according to the present embodiment,
A diaphragm device 2 that adjusts the amount of passing light according to the control signal CTL.
A CCD 3 that receives light that has passed through the diaphragm device 2 to generate an electric signal having a level corresponding to the amount of received light; a sampling circuit 4 that performs sampling processing on the electric signal; A signal processing circuit 5 that obtains a video signal by performing the processing described in 1), a comparator 6 that compares the video signal level with a preset threshold value Vth at the timing of the sampling processing, and outputs a signal corresponding to the difference. Output signal S6 of comparator 6 and control signal C
Adder 10 for obtaining the difference from TL and outputting it to the integrating amplifier 8
And a holding amplifier 11 which holds the output signal S8 of the integrating amplifier 8 during the input period of the holding signal S92 and outputs it as a control signal CTL to the diaphragm device 2 and the adder 10 when the holding signal S92 is stopped. Since the control circuit 9a that outputs the holding signal S92 to the holding amplifier 11 is provided so as to hold the input signal during the sampling period, over-throttle and under-throttle do not occur for control with a long cycle, and the hunting phenomenon occurs It is possible to realize an imaging device that can prevent the occurrence of

[0020]

As described above, according to the image pickup apparatus of the present invention, it is possible to prevent the occurrence of the hunting phenomenon without the occurrence of the over diaphragm and the under diaphragm.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an image pickup apparatus according to the present invention.

FIG. 2 is a timing chart for explaining the operation of the device of FIG. 1;

FIG. 3 is a waveform diagram for explaining the operation of the apparatus of FIG.

FIG. 4 is a block diagram showing a configuration example of a conventional imaging device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Condensing lens 2 ... Aperture device 2a ... Drive motor 3 ... CCD 4 ... Sampling circuit 5 ... Signal processing circuit 6 ... Comparator 7 ... Comparison threshold setting device 8 ... Integrating amplifier 9a ... Control circuit 10 ... Adder 11 ... Holding amplifier

Claims (1)

(57) [Claims] 1. A diaphragm means for adjusting the amount of light passing therethrough according to a control signal, an image sensor for receiving light having passed through the diaphragm means, and an electric signal having a level according to the amount of received light, and the image sensor. Sampling means for sampling the electric signal, comparing means for comparing the electric signal level subjected to the sampling processing at a sampling timing with a preset signal level, and outputting a signal according to the result, and the comparing means. Calculating means for obtaining the difference between the output signal of the control signal and the control signal, integrating means for performing integration processing on the output signal of the calculating means, and holding the output signal of the integrating means during the input period of the holding signal, If the signal input is stopped, the signal holding means for outputting to the diaphragm means and the arithmetic means as the control signal, and the next sampling period , An image pickup apparatus and a control means for said holding signal to hold the input signal to output to said signal holding means.